COLLABORATIVE RESEARCH: Were there "too many" browser species worldwide in local faunas of the Early Miocene? Testing a global hypothesis using the Australian fossil mammal record

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COLLABORATIVE RESEARCH:Were there "too many" browser species worldwide in local faunas of the Early Miocene? Testing a global hypothesis using the Australian fossil mammal record - Christine Janis, Brown University and John Damuth, University of California, Santa BarbaraIs there evidence for a previously unrecognized worldwide change in terrestrial ecosystems approximately 12 million years ago? The PIs hypothesize that a striking pattern that they observed first in the history of the mammal faunas of North America may be one that is actually observable throughout the globe. This project will test this hypothesis by determining whether the same pattern occurred contemporaneously in the fossil record of Australia. Previous research showed that before 12-10 million years ago in North America, many ecological communities contained exceptionally high numbers of species of browsing ungulates (large leaf-eating herbivores)up to three times the numbers seen in vegetationally comparable modern-day habitats. In fact, the numbers of browser species in some places exceeded even those for modern tropical rainforests the present-day habitats with the highest biodiversity of browsers. No other members of these mammal faunas showed any elevated or unusual biodiversity, and faunas younger than 12-10 million years show only "normal" numbers of browser species (by today's standards). Why the older habitats were sometimes able to support what today would be impossibly high numbers of browsers is currently unknown. However, evidence suggests that some European and African faunas from before 12 million years ago also showed "too many" browsers, which in turn suggests a global cause. This project will answer the question of whether there were also "too many" browsers in the well-documented mammalian fossil record of Australia, and, if so, whether this phenomenon disappeared at about the same time as it did in North America. Study of museum collections from Australian localities will allow determination of the numbers of browser species at different times, based on morphology and wear of the teeth. Australia's distinct fauna and environmental history will provide a robust test of whether "too many browsers" was a global occurrence. If it wasn't, then we must look for regional or local causes; but if the global hypothesis is supported then a worldwide phenomenon becomes more likely and these results will guide and motivate the subsequent search for a global cause. The project's results will have implications not only for global environmental history and climate change, but also for any methods that attempt paleoecological interpretations for faunas older than 10 million years that use modern mammal faunas as an environmental proxy. This project will be a new international collaboration and will involve students and postdoctoral researchers.